Keep sent messages visible until received

AGENTS.md

@@ -415,3 +415,12 @@ belongs in `~/.claude/TOOLCHAIN.md` or `~/.claude/MACHINE.md` instead.
   shape: the `markdownIn` scan that decides *what* to parse ran before the
   hop to `Dispatchers.Default`. The shape to watch for is a `withContext`
   that wraps the *fetch* and leaves the work done with the result outside it.
+- **A transcript snapshot cannot survive a suspension and then be assigned.**
+  `loadOlderPage` joined its page to `items`, suspended while `warm` parsed
+  markdown, and then assigned the joined snapshot. An SSE event arriving in
+  that gap appeared and vanished; reopening brought it back because the
+  transcript and cache had it all along. Warm against a candidate if needed,
+  then join against the current `items` and assign without another suspension.
+  Also keep the page's original `oldestSeq`: a stream reset while the fetch or
+  warm is suspended makes the page stale, and it must be discarded rather
+  than joined into the reset window.